The present invention relates to a new and improved sheet material handling apparatus and more specifically to a sheet material handling apparatus in which sheet material is transferred from a feed drum to a conveyor.
Through a process of trying various speed relationships in known sheet material handling apparatus, it has been determined that when sheet material is initially fed to a conveyor by a feed drum, the speed of movement of the sheet material should nearly match the speed of movement of pusher elements in the conveyor. However, in order to maximize performance of the sheet material handling apparatus, it is also desirable to have a greater distance, as measured along the periphery of the feed drum, between sheet material gripper elements on the feed drum than between pusher elements on the conveyor.
Thus, in order to maximize the performance of a sheet material handling apparatus, it has been determined that the pusher elements in the conveyor should be spaced apart by about two inches more than the maximum length of a sheet material article. However, the gripper elements on the feed drum must be spaced apart along the periphery of the drum by approximately five inches more than the length of the sheet material article. This results in a velocity mismatch between the feed drum and the conveyor. This velocity mismatch is not acceptable for high speed operation.
It has previously been suggested that the velocity of the feed drum and/or the conveyor be varied to eliminate the velocity mismatch between the feed drum and the conveyor. This has resulted in the use of relatively complex speed control devices. One such speed control device is disclosed in U.S. Pat. No. 4,993,702 in which a planetary gear system is utilized to vary the speed of a feed drum. Other known speed control devices for use in sheet material handling systems are disclosed in U.S. Pat. Nos. 2,192,916; 4,132,403; and 4,290,595.